WHAT ARE SOME OF THE MOST PREVALENT STANDARDS IN THE MARKET FOR GROUNDING FACILITIES, OTHER THAN THE BASIC REQUIREMENTS OF THE NEC?​

Most telecom companies have their own internal standards (typically 5 ohms or less) which are derived or related from industry-wide telecom standards such as Telcordia (formerly Bellcore) and Motorola R56. These standards are also influenced by equipment vendors such as Nortel and Lucent whose warranties typically require 5 ohms or less. In addition, telecom standards apply to data centers and any facility where communications equipment is installed. Since facilities where data centers and communications equipment are pervasive, the telecom standards frequently become the functional default standards for all facilities.​

The IEEE (“Institute of Electrical and Electronic Engineers”) proposes the following as a guideline for grounding: “The maximum 25-ohm value of the NEC “should not be interpreted to mean that 25 ohms is a satisfactory level for a grounding sys-tem.” IEEE Std. 142-1991 (4.1.2) The IEEE goes on to say that: “Resistances in the 1 – 5 ohm range are generally found suitable for industrial plant substations, buildings and large commercial installations.” IEEE Std. 142-1991 (4.1.2)​

The National Electrical Manufacturers Association (NEMA) gives its own general guideline that “As a rule of thumb, an effective ground for lightning and surge protection purposes should be somewhere around 10 ohms.” NEMA also makes the point that “More important than the absolute value of the ground resistance, is to ensure that all the equipment in the facility is referenced to an equi-potential ground plane through adequate bonding. By ensuring this, all separate pieces of equipment will raise to the same potential during a surge condition.” The latter is one of the objectives of a Lyncole Grounding Survey or Grounding System Compliance Testing.